MICROPHTHALMOS AND NANOPHTHALMOS

 

MICROPHTHALMOS:

A congenital condition in which the affected eye is smaller at birth.

(Less than 15mm in greatest diameter. Normally the diameter varies from 16-19mm at birth.)

PLEASE ALSO VISIT THE OTHER POST ON NANOPHTHALMOS=

https://ourgsc.blogspot.com/2026/04/nanophthalmos.html

TYPES:

1. PURE MICROPHTHALMOS alone (NANOPHTHALMOS/SIMPLE MICROPHTHALMOS): Eye is smaller than normal size, but there are no other gross abnormalities, except for a high lens/eye volume.
2. Microphthalmos with CYST
3. Microphthalmos associated with other SYSTEMIC ANOMALIES, eg. In Trisomy 13 and congenital rubella.

1

Greek= nanos= Dwarf

DEFINITION: Represents an eye reduced in volume, but otherwise grossly normal in form and function.

Male:Female ratio= 1:1.

Bilateral, in cases of general dwarfism.

In unilateral cases the affected side of the body and face is undeveloped.

Inheritance: Sporadic/AD/AR

CLINICAL FEATURES:

1. Narrow palpebral fissure with deeply set eyeball in small orbit.
2. Marked hypermetropia (+18 to 20 D)
3. Lesser hypermetropia, emmetropia or myopia (occasionally, up to -20D) can occur depending upon the shape of the cornea and lens.
4. Usually, the visual acuity is good. Spectacles resemble aphakic glasses.
5. Anterior chamber angle: In young patients, the angle is open with prominent iris convexity. Progressive anterior chamber shallowing and narrowing of angle occurs with the onset of angle closure glaucoma during the 4^th-6^th decades of life.

Lens:Eye Volume ratios:

Lens volume= 4/3AB (A= ½ thickness of lens) (B=radius of globe)

Eye volume= 4/3R (R= radius of globe)

The lens:eye volume is greater (10-32%) in nanophthalmic eyes, compared to normal eyes (where it is 3-4%).

CLASSIFICATION OF NANOPHTHALMOS ON GONIOSCOPY AND IOP:

(Use pediatric goniolens if corneal diameter is reduced)

CATEGORY 1	Angle completely open with marked iris convexity. IOP= ≤ 20mmHg	Management= Observation at 3-4 monthly intervals.
CATEGORY 2	Angle appears partially closed. IOP= ≤ 20mmHg	More frequent observations. Treatment is initiated when there is evidence of progression in angle closure.
CATEGORY	Angle partially or totally closed. IOP= > 20mmHg

 

TREATMENT:

1. MEDICAL
2. LASER
3. SURGICAL

 

MEDICAL:

• Steroids to reduce choroidal effusions which cause angle closure. Oral Prednisolone in the dose of 1-2 g/kg BW/ day, followed by tapering regimen.
• Pilocarpine= Apparently the mainstay of therapy. Start with 1% four times daily (QID), then increase to higher dose (upto 4%) and frequent administration (2 hourly). However, the response is unpredictable.
• Mydriatic and cycloplegic therapy= Cycloplegics → tighten the zonules→ lens-iris diaphragm moves posteriorly→ deepens anterior chamber, reduces relative pupillary block→ restores normal pathway for aqueous flow anteriorly.
• Beta blockers, carbonic anhydrase inhibitors, and sympathomimetics = decrease aqueous production.
• Hyperosmotic agents can be used for short-term control of IOP during acute attacks.

LASERS:

• Iridotomy
• Iridoplasty (Gonioplasty)= low power argon laser therapy to contract the peripheral iris stroma → flattening iris → widening of angle.

SURGICAL STRATEGIES:

• Prophylactic posterior segment surgery= Posterior scleral resection ± posterior sclerectomy.
• Vortex vein decompression.
• Prophylactic anterior segment surgery= Anterior sclerotomies.
• Cataract surgery= Surgical pearls to improve cataract surgery outcomes include: anterior vitrectomy, medical dehydration of the vitreous and scleral lamellar resection. 

Glaucoma surgeries=

• Surgical peripheral iridectomy (PI).
• Trabeculectomy
• Cyclocryotherapy and other cyclodestructive procedures.

Nanophthalmos showing thick sclera